Medieval forge, progress.

I'm finally making some solid progress on the forge I designed this spring. Currently I'm working on the bellows, and today I'm more specifically working on the valve system. The smaller valve at the mouth of the bellow will prevent air to be sucked from the fire pot and also stop any sparks from entering the bellow itself and damaging it. The design of the bellows is taken directly from the "De Re Metallica" by Georgius Agricola, written in the XVIth century. http://www.gutenberg.org/files/38015/38015-h/38015-h.htm